Colorants used in inkjet recording apparatuses may be classified as dyestuffs or pigments. Dyestuffs are used in materials to be dyed, such as fibers, leathers, furs, and papers, and provide considerable fastness in daylight, washing, friction, etc. In contrast, pigments are used in coloring matters in the form of fine particles, which are directly adhered to the surface of materials by physical means, e.g., adhesion, etc.
Dyestuffs may be dissolved in aqueous solvents. Water-soluble dye-type inks have excellent long-term storage stability, are capable of maintaining their homogeneity, and have clear color and brightness, but suffer from poor waterfastness, light resistance, etc. In contrast, pigments are generally insoluble in aqueous solvents. Thus, it is important to homogeneously disperse fine particles of pigments in aqueous solutions and maintain the dispersed state without re-aggregation. Pigment-type inks have high optical densities (OD) and excellent waterfastness and light resistance but have poor color clearness and long-term storage stability compared to dye-type inks. In addition, pigment-type inks produce images having poor dry characteristics and wet rub fastness.
During color printing (multicolor printing) with either dyestuffs or pigments, however, bleeding at interfaces of each color may occur, thereby reducing the clearness of the images. Thus, there is a need in the art to develop ink compositions having excellent storage stability, which is an advantageous characteristic of the water-soluble dye-type inks, and good waterfastness, which is an advantageous characteristic of the pigment-type inks, along with improved printing gloss, rub resistance, and without bleeding at interfaces of each color.